BAFF binds to the tumor necrosis factor receptor-like molecule B cell maturation antigen and is important for maintaining the peripheral B cell population

The tumor necrosis factor (TNF) family member B cell activating Factor (BAF F) binds B cells and enhances B cell receptor-triggered proliferation. We f ind that B cell maturation antigen (BCMA), a predicted member of the TNF re ceptor family expressed primarily in mature B cells, is a receptor for BAFF . Although BCMA was previously localized to the Golgi apparatus, BCMA was f ound to be expressed on the surface of transfected cells and tonsillar B ce lls. A soluble form of BCMA, which inhibited the binding of BAFF to 3 B cel l line, induced a dramatic decrease in thr number of peripheral B cells whe n administered in vivo. Moreover, culturing splenic cells in the presence o f BAFF increased survival of a percentage of the B cells. These results are consistent with a role for BAFF in maintaining homeostasis of the B cell p opulation.